1. Field of the Invention
The present invention relates generally to the field of magnetically sensitive sensors. The present invention relates particularly to a sensor having a magnetoresistive (MR) bridge array optimized for reading fine pitch ring magnets with high air gap at low gauss levels.
2. Description of the Related Art
MR bridges have been proposed before for sensing ring magnets. For example, see Durable and Multifunctional Magnetic Rotation Sensor for Rotary Encoders, Sei et al., IEEE "Transitions on Magnetics", Vol. mag-23, No. 5, pages 2185-2187, (September 1987), and Integrated MR Sensors for Automobile, Akiyama et al., IEEE "Transactions on Magnetics", Vol. 30, No. 6, pages 4617-4619, November 1994.
However, Applicant is unaware of any practical commercial application of MR bridge and ring magnet which has been optimized for sensing at low gauss and high air gap applications for the sensing of fine pitch, 20 to 50 pole pair, ring magnets. This scenario is particularly important for automobile wheel speed sensing which figures prominently in anti-lock brake systems, anti-slip drive systems, power-assists, and other stability systems on modern automobiles.